Rare earth oxides (REO) are frequently used as catalysts or catalyst supports due to their high catalytic activity, good thermal stability, and oxidation resistance. Though there have been many reports on the synthesis of high surface area REO materials, attempts to make pure, monolithic REO aerogels via the simple epoxide-assisted sol-gel method remain limited. Typically, this technique uses a metal chloride as the precursor in an ethanolic solution, which upon the addition of an organic epoxide forms a gel. Unfortunately, the use of the chloride precursor results in formation of a significant oxychloride fraction in the REO aerogels that is extremely difficult to remove (Clapsaddle et al., J. Sol-Gel Sci. Technol., 2012, 64:381-389). Moreover, the presence of chlorine in the REO aerogels leads to a poisoning effect in catalysis applications and can extinguish photoluminescence. Alternatively, chlorine-free methods would produce precipitate rather than monolithic aerogels.
The synthesis of contaminant-free, monolithic REO aerogels via epoxide-assisted sol-gel method remains a significant challenge.